A portable ball throwing machine is described in British Patent Specification No. 2,053,699 in the name of Rallymaster Inc., which was filed claiming priority from a U.S. application Ser. No. 59,984, filed on July 23, 1979 in the name of J. S. Haller, now U.S. Pat. No. 4,237,851. This is a battery operated machine in which balls are supplied from a helical ball track to a firing track. A ball striker is cocked by a motor against the force of an adjustable spring. When the striker is positioned over-center, the striker rapidly rotates striking the ball. A one-way clutch mechanism is included in the gear train between the motor and ball striker, so that the kinetic energy remaining after the ball is launched is utilized to begin cocking the striker for the next cycle of operation.